Control means



W. C. KEERAN CONTROL MEANS April 9, 1963 Filed DeC. 24, 1958 Arroz/Jes@W. C. KEERAN CONTROL MEANS April 9, 1963 Filed Dec. 24, 1958 3Sheets-Sheet 2 INVENTOR WML/AM 6I K55/ZAM #Tram/5 s W. C. KE ERAN April9, 1963 CONTROL MEANS 5 Sheets-Sheet 3 Filed`DeG. 24, 1958 INV ENTORW/LL/A/v/ C. K55/ZAM United States Patent O 3,055,3l79 CNTRGL MEANSWiiliam C. Keeran, Evanston, lili., assigner, by rnesne assignments, toVapor Corporation, Chicago, Ill., a corporation otr' Delaware Filed Dec.2d, 1953, Ser. No. '782,967 8 Ciaiins. ifi. 3l7--124) The presentinvention relates to control means, and more specifically to controlmeans incorporating a light sensitive element for turning on and off, orotherwise, controlling sources of illumination.

Light control means have been extensively employed in connection withstreet lighting systems, advertising signs and the like. They also haveapplication in connection with warning lights on radio and televisiontowers, navigation beacons, and illumination of service stations,parking lots, factory areas, viaduct underpasses, outdoor telephonebooths, et cetera. It would be desirable to provide light control meansfor automatically turning on street lights, flood lights, warning lightsand advertising lights whenever illumination is needed at a selectedpredetermined degree of darkness regardless of the particular time ofday, which control means will also automatically turn off or otherwiserender ineffective the illumination when it is not needed. Such deviceor control means should be very sensitive so that a small change inlight of the order of less than one half foot candle will causeoperation of the device. In addition to being very sensitive, suchdevice must have 'a long life and, furthermore, it should be capable ofbeing replaced in a very simple manner. Moreover, should any portionthereof fail, it should fail with the light control switch thereof inclosed position so as to supply the necessary illumination Whetherneeded or not. Such a device should have a very low power consumption,preferably less than one half watt exclusive of the load circuitcontrolled by the device. Additionally, `such a device should be capableof being adjusted so that the light level at which the control operatesmay be varied at will, but, once adjusted to some selected setting, itwill operate uniformly thereafter. Although such a device must be verysensitive to light changes, it must be insensitive to momentary andextraneous sources of light such as lightning, automobile headlights andthe like. Furthermore, since such control apparatus must be capable ofbeing located in exposed places in a variety of atmospheres, it shouldbe completely sealed against exposure to atmosphere and yet protected sothat snow or dirt or the direct rays of the sun cannot adversely affectthe light sensitive element of the device.

Accordingly, it is an object of the present invention to provide animproved control means incorporating all of the desirablecharacteristics enumerated above.

It is another object of the present invention to provide a new andimproved illumination control means for automatically turning onillumination when needed in response to a particular level of ambientillumination and automatically turning off illumination when not needed.

It is another object of the present invention to provide an improvedlight control means which is simple and compact, which will give longyears of service and yet which involves a disposable unit which can bereplaced in a simple manner similar to replacing a light bulb or thelike.

A still further object of the present invention resides in a lightcontrol means which employs no elec-tronic tubes or equivalent devicesand yet which is sensitive to very small changes in illumination of theorder of less than one half foot candle.

Another object of the present invention resides in the 3,85,l'i"iiPatented Apr. 9, 1963 ICC provision of a light control means which isaffected solely by changes in illumination and which is unaffected bychanges in ambient temperature such as are encountered in climates wherethe temperature may be very hot in one season of the year and very coldin another.

Further objects and advantages of the present invention will becomeapparent as the following description proceeds, and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecication.

For a better understanding of the present invention, reference may behad to the accompanying drawings in which:

FIG. 1 is a perspective view of a control unit embodying the presentinvention;

FIG. 2 is an enlarged elevational view, partly in section, of thecontrol unit of FIG. l;

FIG. 3 is a greatly enlarged fragmentary View of a `small portion ofFIG. 2 more clearly to illustrate the features of the present invention;

FIG. 4 is a fragmentary sectional view taken on line 4--4 of FIG. 2,assuming that FIG. 2 shows the complete structure;

FIG. 5 is an enlarged fragmentary sectional view taken on 'line 5 5 ofFiG. 2, again assuming that FIG. 2 shows the complete structure;

FIG. 6 is a fragmentary sectional View taken along line 6-6 of FIG. 5,assuming that FIG. 5 shows the complete structure, and with a portion ofthe housing cut away;

FIG. 7 is a sectional view through the solenoid controlled switchembodied in the unit of FIG. l and generally comprises a reducedsectional view taken on line '7 7 of FIG. 5, assuming that FIG. 5 showsthe complete structure;

FIG. 8 is a sectional view taken on line S- of FIG. 5, also assumingthat FIG. 5 shows the complete structure;

FIG. 9 is 'a sectional view taken on line 9 9 of FIG. 2, assuming thatFIG. 2 shows the complete structure;

FIG. d0 is a sectional view taken on line IQ--Itl of FIG. 2, assumingthat FIG. 2 shows the complete structure;

FIG. 11 is a sectional view taken on line ill-11 of FIG. 5, assumingthat FIG. 5 shows the complete structure;

FIG. l2 is a schematic circuit diagram showing the electrical circuitembodied in the particular modification of FIG. l; and

FIG. 13 is a circuit diagram similar to FIG. 12 illustrating anotherapplication of the present invention.

Brieily, the present invention comprises a small compact sealed housinghaving means to plug the same into an electric circuit to be controlledthereby, which housing includes a light sensitive element, currentcontrol means operated thereby, together with suitable time delay means,and which may or may not include a high current carrying switch inaddition to the aforementioned current control means, depending upon theparticular application. The time delay means also embodies temperaturecompensation means so as to make sure that the device operates the sameregardless of the ambient temperature likely to be encountered.Relatively small changes in electrical current caused by the lightsensitive element are utilized to operate the current control meansdirectly without the requirement of any electronic tubes, transistors orthe like. Additionally, except for switch contacts, no moving parts areinvolved. Novel sealing means are incorporated so that the entire deviceis sealed against the entrance of dirt, moisture or other foreignmatter.

Referring now to the drawings, there is illustrated in G. l a lightcontrol means or a unit generally designated by the reference numeral2t) which is very compact and which comprises a base 21 sealed to atubular member 22 which forms part of a suitable housing within which ismounted a light sensitive element generally designated at 23. in orderthat illumination may reach the llight sensitive element 23, the upperpart of the tubular housing 22 is enclosed by a transparent ortranslucent member or window 24 which is actually illustrated as acup-shaped member hermetically sealed to the upper end of `the tubularmember 22, as will be described in greater detail hereinafter, therebyto define with the base 2 the complete housing. For the purpose ofcontrolling the effectiveness of the window provided by the transparentor translucent member 24 and, consequently, for controlling the lightlevel at which the light sensitive element 23 is rendered effective,there is provided a light level control element or cap 25 in the form ofan adjustable cup-shaped cover member which may be selectively adjustedto decrease or increase the quantity of ylight reaching lthe lightsensitive element 23, as the case may be.

Aside from the housing referred to above which is de- I:lined by theelements 2i, 22 and 24, the light control means of the present inventionessentially comprises the light sensitive element 23, a time delay unitgenerally designated at 26, best shown in FIG. 12 of the drawings, andsuitable current control means which may comprise a snap-acting switch27' operated by the time delay unit 9 26. The switch 27 may be the solemeans for controlling the electrical circuit, or, as illustrated in FIG.l2, a suitable electromagnetic switch generally designated at 28 may beprovided, the energization of which is controlled by the switch 2'7.

In order that the light control means 2t) of the present invention mayeffectively comprise a throw away unit which can readily be replaced, aplurality of prongs 29, 39 and 311 are associated with the base 2 whichare arranged in the form of a conventional three-prong twist lock typeelectrical connector so that they may readily be inserted in a suitablesocket well known in the art. It should be understood that other typesof connection may also be employed. As was mentioned above, the iightcontrol means or unit 20 may include a high cur rent switch 28 capable`of carrying very high currents for controlling illumination of theorder of 3000- watts. However, 4for low current applications such switchmay be dispensed with and a simple snap-acting switch 27 alone may beemployed. In an arrangement for controlling very high currents where ahigh current switch 28 is incorporated, a unit built in accordance withthe present invention was less than nine inches in ever-all height, andthe tubular member 22 had an outer diameter of only one andthree-quarters inches, while the base 21 had a diameter or lthreeinches.

Considering now, iirst of all, the housing and sealed construction ofthe light control means of the present invention, the base 21 maycomprise any suitable member such as a casting of aluminum or similarmaterial, which casting has an enlarged annular iiange 2id and a centralcylindrical portion 2lb of an outer diameter so as to snugly iit theinner diameter of the tubular member 22. The underside of the base 21,as best shown in FIG. l of the drawings, is provided with a recess onthe underside thereof to receive a molded insulating member 33 which hasthe contacts 29, 30 and 3ft suitably molded therein. The element 33` isessentially available on the market as a commercial element and meetscertain specifications so as to fit standard sockets of the twist locktype. The portion 2lb of the base 2l, which also is illustrated ashaving a shallow recess on the top thereof opposite the recessaccommodating the member 33, is provided with a plurality of openings 35(FIG. 9) through which insulated conductors 36, 37 and 33, best shown inFIG. 12 of the drawings, may extend for electrical connection with theterminals 29, 3d and 3l, respectively. As illustrated in the drawings,the conductors 36 and 37, which `for `certain applications must carryrelatively high currents, are substantially larger than the conductor38, which is merely required to carry a relatively low control current.

To permit a sealed connection to be made between the base 21 and thetubular housing 22, the portion 2lb of the base 2l is provided with twospaced apart circumferential recesses 39 and 4d, respectively, therecess 39 being immediately adjacent the ilange portion 21a, while therecess titl is adjacent the top of the portion 2lb as viewed in FIG. 2of the drawings. The recess lil is adapted to accommodate a sealing ringdi which is preferably the well-known l(Zt-ring, while the recess 39 isernployed to permit securing the base 2i to the tubular housing in afinal assembly step. When all the parts are assembled and the electricalconnections are made, the portion 2lb of the base 2l is telescoped intothe lower end of the tubular member 22, a seal being provided by thesealing ring dit. The lower end of the tubular member 22 lis thendeformed as indicated at 22a as by a rolling or peening operationwhereby the portion 22a is `forced into the circumferential recess 3g,thus securing the tubular member 22 to the base 21 in sealedrelationship therewith.

For the purpose of insuring a sealed arrangement at the upper end of thetubular member 22 which will prevent moisture or the like from enteringthe sealed housing provided with the present arrangement, thetransparent or translucent cup-shaped member 24, which may be formed ofglass or a suitable transparent or translucent plastic, is provided witha very small annular iiange 24a around the outside of the open end ofthe member 24. The member 22 is `furthermore provided with an annulardeformation 22b slightly below the open upper end thereof which providesan annular `shoulder for supporting a ring 42 of L-shaped cross section,as clearly shown in FIGS. 2 and 3 of the drawings. A suitable sealingring 43, preferably an 'O-ring, is disposed in the recess defined by theannular member or ring 42 of l.- shaped cross section. When thecup-shaped member 24 is seated on the O-ring as shown in FlG. 2 of thedrawings, the upper end of the tubular member 22 is peened over asindicated at 22C as by a rolling operation or the like, whicheifectively forces the rim including the tlange 24a of the cup-shapedmember 2d into sealing engagement with the IO-ring d3, which O-ring isalso forced into sealing engagement with the interior sur-face of thetubular member 22. There is thus provided in a very simple manner anhermetic seal at the upper end of the tubular member 22.

To provide means for adjusting the light control and thus control theeifectiveness of the window provided by the cup-shaped member 24, thereis provided the adjustable light level control element or cap 2S whichmay be formed of aluminum or other suitable material. As illustrated,the transparent or translucent cup-shaped member 24 is provided with anopening 44 in the closed end thereof for receiving a hollow stud membert-a' which has the closed and sealed end thereof extending into thecup-shaped member 24?. This stud 15 is secured in sealed relationshipwith respect to the opening as by means of resilient washer or gasketmembers 46 and 47, one on either side of the wall defining the closedend of the cup-shaped member 24. A flange 45a is provided on the stud 4Sand a washer 48 is pressed over the lower por tion of the stud 45 andsuitably secured thereto as by welding so as to compress the washers 46and d'7 against opposite sides of the end wall of the member 24. Theinterior of the hollow stud member iii is threaded as indicated at 49 toreceive an adjusting screw 5t) secured to the inside of cap and disposedalon-g the longitudinal axis thereof. The cap 25 is somewhat conical inshape and is larger in diameter than the cup-shaped member 24. Bysuitable rotating the element 25, more or less of the cup-shaped member24 is exposed, and consequently the window through which light issupplied to the light sensitive element 23 is selectively controlled.Preferably, the member 25 is knurled or roughened on the exteriorsurface as clearly Iindicated in FIG. 2 of the drawings to make for easymanual adjustment.

In order to make sure that the particular selective adjustment of themember 25 remains at whatever setting it is initially set, the sealingwasher 46 is of such a diameter as to be slightly larger than the innerdiameter of the adjustable member 25' as clearly indicated in FIG. 2 0fthe drawings, thus providing a frictional drag. The member 46,therefore, performs two functions: rst, to seal the transparent member2d against the entrance of moisture at the opening 44 and, second, toinsure that the light control member 25 remains yfixed at any selectedadjustment.

In View of the detailed .description included above, it will beappreciated that there has been provided a completely sealed housing forincorporating the light control means of the present invention.`liiurthermore, the sealed unit may be connected into any suitableelectric circuit by a simple plugging operation as will be readilyunderstood by those skilled in the art, thus permitting readyreplacement.

Before considering how the elements of the light control device of thepresent invention are supported within the sealed housing heretoforedescribed, the individual components of the device will first beconsidered in detail with reference to both the schematic diagram orFlG. l2 and the structural disclosures thereof. First of all, the lightsensitive element 23 has been schematically designated in FIG. 12 as aphotcconductive cell whose electrical conductance changes underillumination. Thus, FIG. 12 indicates that the light sensitive elementis ef- -fectively a variable resistor. Although a photoconductive cellhas `been found to be especially desirable as far as the presentinvention is concerned, other types of light sensitive elements may beemployed. A light sensitive element of the photoconductive typegenerally ernploys a chemical element which lies in the border-landbetween conductors and insulators. As the light imposed Iupon thechemical element increases in intensity, the resistance thereofdecreases, thus permitting more current to how through the lightsensitive cell which is connected in a circuit across a suitable sourceof voltage. The particular chemical element employed for the lightsensitive element 23 forms no part of the present invention, but itmight comprise cadmium sulphide, cadmium selenide, lead sulphide or thelike. Preferably and as will be described in greater detail hereinafter,the light sensitive element 23 is mounted below the bottom of thecup-shaped member 24 as shown in FIG. 2 of the drawings whereby directrays of sunlight are prevented by the tubular member 22 from reachingthe element 23 except through the window defined by the cup-shapedmember 24. The adjustable cap member 25 provides a sort of sun shade,considering vertical mounting of the dev-ice which is desirable, andalso the design is such that snow or dirt cannot accumulate toeffectively close the window provided in the sealed housing.

i A light sensitive element such as 23 is a very fast aeting device and,to all intents and purposes, is almost instantaneously responsive to achange in illumination. It is desired in a light control apparatus thatthe gradual reduction in the level of illumination as it becomes dark inthe evening will cause the device to turn on suitable lights, and whenthe level of illumination increases to a sufficient extent in themorning to turn off such lights. However, since the light control deviceof the present invention is likely to be exposed to extraneous momentarysources of light such as lightning, automobile headlights and the like,there is provided the time delay device 26 which prevents instantaneousoperation of the switch means 27 in response to any change inillumination applied to the light sensitive element 23. In accordancewith the present invention the time delay device 26 comprises twoidentical bimetallic elements 50 and 51 having corresponding endsthereof secured to a suitable insulating support 52. This support isschematically illustrated in FIG. 12, but as shown in the other views ofthe drawings comprises an annular member suitably supported above thebase 21 by a pair of spaced rods 53 disposed parallel with thelongitudinal axis of tubular member 22, as best shown in FIGS. 2, 5, 6,7 and 9 of the drawings. The bimetallic element 5ft has one end thereffastened to the support S2 as by screws 55. Suitable end support means56 may be provided, one on either face of the bimetallic element 50.Similarly, the bimetallic element 5l, which is identical with thebimetallic element 5d, is secured to the support S2 as by fasteningmeans such as -screws 57. A pair of support means 5S, similar to thesupport means 56, are disposed one on either side of the bimetallicelement 5i. The other ends of the bimetallic elements 5f) and 5l notsecured to the support 52 are free and, with equal heating, thesebimetallic elements will be deflected in equal amounts in the samedirection. In other words, the high expansion sides of the bimetallicelements Si) and S1 are similarly orientated so that upon an equalincrease in temperature of the bimetallic elements 50 and 51 they willbe deflected equally toward the left as viewed in FIG. 12 of thedrawings. This arrangement insures that changes in ambient temperaturewill have no effect on the operation of the switch 27 controlled by thetime delay unit 26 or, in other words, the switch 27 is insensitive toambient temperatu're.

Secured to the free end of the bimetallic element Sii is the currentcontrol means 27 illustrated as a snap switch which may be any one ofthe well-known switches operating with a snap action such as arevariously sold as microswitches or the like. The particular snap-actingswitch illustrated in FIGS. 5I 8 and 1l of the drawings is by way ofexample only and comprises an insulated base plate 6i? suitably securedas by rivets 61 to the free end of the bimetallic element Sil. The snapswitch 27 further lincludes a pair of relatively movable contacts 62 and63, the Contact 62 being a stationary contact and the contact o3 being amovable contact. A suitable overcenter mechanism including the spring 64will insure that the contacts 62 and are made and broken with a snapaction. The switch 27 has been specifically illustrated as of thenormally open type, but for certain applications as describedhereinafter it might equally well comprise a normally closed typeswitch.

Secured to the `free end of the bimetallic element S1 is a suitableinsulated switch operating member '70 which is preferably adjustablymounted for movement along its longitudinal axis in a Z-shaped bracket72 riveted as indicated at 73 to the free end of bimetallic element Sil.The insulated actuating member 7o is preferably mounted on the end of anadjusting screw 7d threadedly mounted in a suitable opening in Z-shapedsupport 72. A suitable lock nut 75 is provided for locking adjust-ingscrew 7d in any selected position. The insulating switch actuatingmember 7d is adapted upon movement of the free end of the bimetallicelement 51 towa-rd the free end of bimetallic element 5h to actuate thesnap switch 2.7.

It will be apparent from the above description that since the bimetallicelements Sil and 51 move together in response to ambient temperaturechanges, operation of the switch 27 could not be accomplished withoutadditional means. To this end there is provided a heating element `orresistance heater '76 surrounding the bimetallic eleassalito V. d' mentl, which heating element is electrically connected in series with thelight sensitive element 23. A suitable insulating layer 77 surroundingan intermediate portion of ybirnetallic element 5l, as best shown in FG.5 of the rawings, insulates heater 76 from bimetallic element 5l. Topermit ready electrical connection with resistance heater 76, a pair ofband terminals 78 and 79 are secured around the layer "I7 at either endof heating element 76'. As illustrated in the drawings, a suitableconductor 80' interconnects the light sensitive element 23 (FlG. 4) andthe heating element terminal 78, While the other terminai 79 of theheating element is connected by a conductor Sl directly to the conductor3S. The other terminal of the light sensitive element 23 is connected bya conductor 32 to the conductor 37. Conductor 3S is preferably connectedto ground, while conductor 37 is preferably connected to one side of analternating current source so that ll() volts of O-cycle current arenormally connected across the serially arranged light sensitive element23 and resistance heater 7d. During daylight hours the light falling onlight sensitive element Z3 is such as to decrease its resistancesufficiently to cause a current to flow through the resistor orresistance heater 76. The light sensitive element 2-3 should be such asto be capable of continuously withstanding a maximum of about one halfwatt of electrical energy. The resistance of the heater element '76 mustbe such that regardless how low the resistance of the light sensitiveelement 23 Ibecomes due to high intensity of ambient light, the powerdissipation in the light sensitive element 2,3 will never exceed onehalt watt.

During daylight hours the current flowing in heater element 76 willcause bimetallic element 5l to be dellected toward bimetallic element 56to acuate normally open snap-acting switch 2-7 to the closed position.Preferably, the circuit constants are such that when the light level onthe light sensitive element 23 falls to less than a one half footcandle, and preferably of the order of a one quarter foot candle, thecurrent flowing in heater element 76 will decrease to the point thatbimetallic element 5l will deflect away from element Sti and cause thesnap-acting switch Z7 to open the circuit at contacts 62 and 63. Formany applications the snap-acting switch 27 is capable of performing adirect switching operation on the illumination control circuit, and tothis end the contacts 62 and 63 may be connected directly in thelighting circuit to be controlled. lf this is the case then the switch27 is a normally closed switch instead of the normally open switch `asillustrated. Thus, with the normally closed switch, as the light levelincreases, the resistance of the light sensitive element 23 decreases topermit suilicient current to ow through resistor 76 to heat bimetallicelement 5l, with the result that the normally closed contacts of theswitch 27, which would be required in such case, are opened. However,the present invention has been illustrated particularly for .use with ahigh current carrying switch such as 2S, and under these circumstancesthe switch 27 must have normally open contacts as illustrated. Underthese conditions an alternating current power source indicated at 83 inFIG. l2 would be Connected between terminal 3) of unit Ztl and oneterminal of a lighting load S4. The other terminal of the lighting loadwould be connected to terminal Z9. Also, terminal 3l would `be connectedto the terminal of power source 83 to which the lighting load isconnected.

Considering now the electromagnetic switch 28, it has been illustrated`as a mercury switch of the type shown in Lemp Patent No. 536,811. ltmay, however, comprise the high current switching device disclosed andclaimed in copending Brosseau and Keeran application Serial No. 782,823,tiled concurrently herewith and assigned to the same assignee as theinstant application. Preferably this switch comprises a sealed envelope85 shaped in the form of an inverted Y with a pair of hollow diverginglegs 85a and 317i) connected to an upwardly extending and verticallydisposed hollow leg 85e. A reciprocating magnetic plungto to er 86 isdisposed in the leg tc, which plunger is connected to a bridging contact87. As illustrated, the bridging contact is of U-shaped configurationwith the lower end of plunger connected to the bight of the U, and thelegs 57a and 87!) of the U extending into the hollow legs and h,respectively. "the hollow legs 35a and 85h of the sealed envelope 85contain mercury indicated at 8S to a level slightly below the commonconnection with the upwardly directed leg 85e thus effectively deliningtwo separate mercury pools. The bridging element 87, due to the actionof gravity on it and the associated plunger 256, is normally disposed sothat the legs 87a and 37b are disposed within the two mercury pools thuselectrically interconnecting these mercury pools. Upward movement of thebridging contact d'7 will interrupt the circuit between these pools. Theenvelope S5 may be evacuated or may be iilled with a suitable inertatmosphere such as nitrogen or the like. Electrical terminals ta and 8%(FG. 7), extending into the hollow legs 35a and SSI), respectively, aresealed in the glass envelope 85 and provide the switch terminals towhich electrical connections are made. As illustrated, the terminals 89aand 55% are connected to the conductors 36 and 37, respectively, whichconductors are in turn connected to the terminals 29 and Sti,respectively.

ln order to actuate the magnetic plunger 8d of high current carryingswitch ZS within the sealed envelope S5, these is provided a solenoidwinding 90 surrounding the leg 85C of the envelope S5. The plunger 86and solenoid winding Siti effectively provide an electromagnet foractuating the mercury switch described above. Energization of thewinding 9d will cause the circuit to be broken between bridging contact37 and the mercury pools disposed in hollow legs 85a and Sb of sealedenvelope 35.

To support the electromagnetically actuated high current carrying switch28 within the small sealed housing described above, the annular support5?; is relied upon. As illustrated, the solenoid winding 90 is mountedupon the support 52, with the leg 85e of the sealed envelope 85extending through the central opening 91 in annular support SZ. Asillustrated in FIG. 5 ofthe drawings, support 52 is provided withdiametrically opposed notches 92 to accommodate the diverging legs 85aand iSb of the sealed envelope With this arrangement annular support 52,solenoid winding 9u, arm 85C of the sealed envelope SS and plunger Seare concentrically arranged.

'For the purpose of completing the electrical circuit and as illustratedin FIG. l2 of the drawings, one terminal of the solenoid winding 96 isconnected by a conductor 95 with the switch contact 63, while the switchcontact 62 is connected 'oy the conductor 38 to the grounded terminal3l. The other terminal of the solenoid winding 9i) is connected by aconductor 97 to the conductor 82, which is connected to the powerconductor 37 at the switch terminal The support 52; may be provided withsuitable notches 9S to position the conductors Si), 82, 95 and 97 so asnot to interfere with `the tubular member 22. t

In view of the detailed description included above, the operation of thelight control means of the present invention will readily be understoodby those skilled in the art. Where the lighting load involves relativelyhigh currents, the circuit as shown in FIG. l2 will be employed. Duringnormal daylight hours the current flowing through heating element '7owill be suiciently high due to the low resistance of the light sensitiveelement 23 as to cause the bimetallic element 5l to deflect and closethe sna acting switch 26. rlhis will result in energization of thesolenoid winding 9i?, with the result that the mercury switch is movedto deenergize the lighting load When the light level decreases to apredetermined level, for example, one half foot candle, the resistanceof the light sensitive element 23 increases, thus increasing theimpedance to current flow in the circuit including heater element '76whereby bimetallic element 5l cools and deilects in a direction topermit switch 27 to open. Openaosaire ing of switch Z7 deenergizes thesolenoid winding 90 to cause the electromagnetically actuated mercuryswitch 23 to close due to the action of gravity upon the plunger 86 andbridging contact 87.

For applications where only a relatively low current lighting load is tobe employed, the solenoid operated switch 28 and the conductors 9S and97 will be completely eliminated, and the switch 27, which now must be anormally closed switch, may be used directly to control the lightingcircuit. Under these conditions, for the arrangement shown in FIG. 12the `contact terminal 29 will be omitted and the power and load will beserially connected across terminals 30 and 31.

There are applications of the present invention where it may bedesirable to energize the lighting load when the light level falls to apredetermined value but to turn off the lighting load before daylightagain arrives. For example, in the advertising field, the trafc aftermidnight or one oclock in the morning may be sufficiently low as not tojustify keeping an advertising sign lighted. In the above mentionedBrosseau and Keeran application there is disclosed and claimed a controlcircuit in which a timing device is incorporated with a switchingdevice. The present invention may also be associated with such a timingdevice and in FIG. 13 of the drawings there is illustrated anapplication of the present invention where it is desired to turn off theillumination at a predetermined selected time. `The corresponding partsof FIG. 13 are designated by the same reference numerals as in thepreceding embodiment. As there illustrated, and in accordance with thedisclosure of the Brosseau and Keeran application, there is added to thearrangement of FIG. l2 a mechanism or clock and ycam arrangementgenerally designated at 19t) which may comprise a conventional electricclock 101, which makes 1 r.p.m. in twenty-four hours. This clock isdrivingly connected, preferably through a slip clutch 192, to a cam 103,which cam is adapted to control a normally open snap-acting switch 194having a xed contact 105 and a movable contact 106. The switch isconnected in series with the c oil 90 and the terminals 30 and 31. Thus,the load circuit may be controlled by closing either the `contacts ofthe switch 27 or the contacts of the cam-actuated switch 104.Preferably, the cam 103 is designed to keep the switch 104 closed for afixed period such, for example, as six hours, after which the switch isagain opened. 'As illustrated, the cam 103 is provided with an indicator16'7 which preferably is visible on the face of the clock 101. Bysetting the indicator 107 to the time of day at which the operatorhappens to be adjusting the mechanism 100, the cam 103 may be caused toclose the circuit at midnight and open it when a fixed period of timehas elapsed. The timer means 100 will thus energize lthe winding 90 ofthe mercury switch 28 at midnight, thus preventing the light sensitiveelement 23 from keeping the lights energized during that fixed period.Obviously, the cam 1153 can be designed to give any span other than asixhour span, which has been chosen by way of example only. Furthermore,by providing the indicator 107, the operator, in setting it to whateverthe time is when the device is set, which is possible by virtue of theslip clutch 102, will be assured of proper adjustment thereof. Thearrangement of FIG. 13 is particularly useful for lighting arrangementssuch as advertising signs where there is no need to have light after apredetermined time, which might also be true of factory parking lots andthe like.

From the above description it will be apparent that there has beenprovided a light control means which requires no electronic tubes,transistors or similar devices, and except for the employment f switchcontacts involves no moving parts. In the event of failure of any of thecomponents, such as the light sensitive cell, the device will fail safein that illumination will be provided. The entire components of thedevice are embodied in a sealed unit which may be thrown away whendefective and replaced by a new unit.

While there have been illustrated and described a particular embodimentof the present invention and applications thereof, it will lbeappreciated that numerous changes and modications will occur to thoseskilled in the art, and it is intended in the appended claims to coverall those changes and modifications as fall within the true spirit andscope of the present invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

v1. Switching apparatus, comprising a hermetically sealed housing havinga 4window wall portion, a photocell mounted in one end of said housingand disposed to intercept at least a portion of the light entering saidhousing through said `window wall portion, said photolcell having anelectrica-l characteristic which varies in accordance with the lightimpinging on said photocell, electromagnetic switching means comprisinga set of relatively movable contacts mounted in said sealed housingbetween said photocell and the other end of said housing, a set ofterminals extending through said housing and electrically connected torespective ones of said contacts, and means mounted within said housingresponsive to said electrical characteristic of said photocell forselectively operating said switching means, said means responsive tosaid electrical characteristic comprising a bimetallic switch actuatingmember and a heater resistor for said bimetallic member, said resistorbeing serially connected with said photocell.

2. Switching apparatus, comprising a generally tubular, hermeticallysealed housing having a window wall portion at one end thereof, aphotocell mounted in said housing in proximity to said wall portion, aswitch mounted in said housing between said photocell and the other endof said housing, means electrically connecting said switch to saidphotocell to cause said switch to be actuated in response to the levelof light impinging on said photocell, a plurality of terminals extendingthrough said other end of said housing, said terminals beingelectrically connected to said switch, and an opaque light adjustingmeans mounted at said one end of said housing for movement along thelongitudinal axis of said housing for controlling the light transmittingeffectiveness of said window wall portion selectively .to adjust thesensitivity of said apparatus` 3. Switching apparatus as set forth inclaim 2 wherein said light adjusting means comprises a cup-shaped memberthreadedly connected to said housing.

4. A light responsive switching device comprising a current responsiveelectromagnetic mercury relay having an operating coil and a set ofnormally closed first contacts, a time delay switch including a set ofsecond contacts and a bimetallic actuating member for closing saidsecond contacts when the temperature of said member exceeds apredetermined value, a heating resistance for said actuating member, aphotocell, means for serially connecting said resistance and saidphotocell across a source of voltage, and means for serially connectingsaid operating coil and said second contacts across a source of voltageso that said normally closed first contacts of said relay are opened andclosed without delay in response to the respective closing and openingof said second contacts, said second contacts closing when the lightimpinging on said photocell is above a predetermined level for a periodsuiiicient to heat said resistance to actuate said member, and openingwhen the light impinging on said photocell is below a predeterminedlevel for a period suflicient to permit said member to return to itsunactuated position.

i5. The switching apparatus of claim 2 wherein means are provided tohold said light adjusting means in any predetermined selected position,which means also serves to seal said housing.

6. Light control means, comprising a base, electrical terminalsprojecting from said base, an electromagnetic switch supported abovesaid base including an insulating support, time delay means dependingyfrom said support including switch means, a light sensitive elementmounted above said support, circuit means for connecting said terminals,said electromagnetic switch, said time delay means and said lightsensitive element into an electric circuit whereby said switch isactuated in response to gradual changes in light level betweenpredetermined limits, a housing cooperating with said. base forenclosing all of said elements except a portion of said base andterminals, said housing including a cup-shaped transparent wall portionat the upper end thereof secured to a tubular member in sealedrelationship therewith to permit illumination to reach said element, andmeans for sealing said housing to said base.

7. The light control means of claim 6 wherein means comprising acircular opaque member adjustably positioned relative to said cup-shapedtransparent member is CJI 1?; provided selectively to adjust thesensitivity of said light control means.

8. Switching apparatus as set forth in claim 2 wherein said lightadjusting means comprises a member threadedly connected to said one endof said housing.

References Cited in the file of this patent UNITED STATES PATENTS2,331,475 Johnson Oct. 12, 1943 2,631,247 Shaw Mar. 10, 1953 2,697,803Eadie Dec. 2l, 1954 2,753,492 Jay July 3, 1956 2,755,392 Garnick July17, 1956 2,898,525 Jacobs Aug. 4, 1959 2,900,520 Frank Aug. 18, 1959FOREXGN PATENTS 159,650 Sweden July 16, 1957

1. SWITCHING APPARATUS, COMPRISING A HERMETICALLY SEALED HOUSING HAVINGA WINDOW WALL PORTION, A PHOTOCELL MOUNTED IN ONE END OF SAID HOUSINGAND DISPOSED TO INTERCEPT AT LEAST A PORTION OF THE LIGHT ENTERING SAIDHOUSING THROUGH SAID WINDOW WALL PORTION, SAID PHOTOCELL HAVING ANELECTRICAL CHARACTERISTIC WHICH VARIES IN ACCORDANCE WITH THE LIGHTIMPINGING ON SAID PHOTOCELL, ELECTROMAGNETIC SWITCHING MEANS COMPRISINGA SET OF RELATIVELY MOVABLE CONTACTS MOUNTED IN SAID SEALED HOUSINGBETWEEN SAID PHOTOCELL AND THE OTHER END OF SAID HOUSING, A SET OFTERMINALS EXTENDING THROUGH SAID HOUSING AND ELECTRICALLY CONNECTED TORESPECTIVE ONES OF SAID CONTACTS, AND MEANS MOUNTED WITHIN SAID HOUSINGRESPONSIVE TO SAID ELECTRICAL CHARACTERISTIC OF SAID PHOTOCELL FORSELECTIVELY OPERATING SAID SWITCHING MEANS, SAID MEANS RESPONSIVE TOSAID ELECTRICAL CHARACTERISTIC COMPRISING A BIMETALLIC SWITCH ACTUATINGMEMBER AND A HEATER RESISTOR FOR SAID BIMETALLIC MEMBER, SAID RESISTORBEING SERIALLY CONNECTED WITH SAID PHOTOCELL.